This research is directed toward an understanding of biological assembly processes which involve participation of molecules not found in the assembled structure. Bacteriophage lambda head assembly is used as a model for these processes. Aspects of viral assembly being studied include the participation of the host cell in assembly, and protein processing reactions that occur during assembly. In order to understand the assembly processes, the detailed structure of the head will be examined by immunoelectron microscopy, with particular emphasis on the head-tail connector, a substructure of the head that has central roles in most of the processes we are studying. The chemical structures of the products of an unusual protein fusion reaction and a protein cleavage reaction that occur during assembly will be examined. Complexes of proteins that are assembly intermediates will be sought and characterized. The groE protein, a host protein that is required for correct head assembly, will be studied in a variety of ways, including how its synthesis is regulated and how it interacts with phage proteins and other host proteins. The lambda early protein Ea10, which is a ssDNA binding protein, will be investigated in an attempt to learn how it is involved in regulating groE synthesis.